Instrument panels installed in the front portion of vehicle compartments, mounting components of the instrument panels, and the like, are designed to meet regulations in terms of shock absorbing characteristics and the shape of protrusions, in an attempt to protect vehicle passengers against shocks upon crash of the vehicles.
In the meantime, a shift lever to be manipulated by a vehicle driver to generate gearshift commands is provided on the instrument panel in the vicinity of the driver's seat, or on an upper surface of a front console located in a central, front portion of the vehicle compartment. The shift lever also needs to be designed to provide desired shock absorbing characteristics, similarly to the surface portion of the instrument panel.
To provide suitably controlled rigidity in the protruding direction of the shift lever upon application of an excessive load thereto, a known type of shift lever includes a shaft portion in the shape of a pipe that is formed of a fiber reinforced plastic material, and a shock absorbing portion provided at an end portion of the pipe. In this case, when an excessive load is applied to a knob of the shift lever, the shock absorbing portion expands and ruptures the end portion of the pipe in the direction perpendicular to the axis of the pipe, thereby to absorb shocks, so that the deceleration experienced by the passenger is limited to be equal to or smaller than its regulation value. One example of this type of shift lever is disclosed in Japanese laid-open Patent Publication (Kokai) No. 9-58288.
In case the shift lever is mounted on the instrument panel, a lever mount bracket, that supports the shift lever, is attached to a base member of the vehicle body located below the instrument panel by a pipe-like connecting member(s) provided between the bracket and the base member. It has been proposed to form the connecting member from a pipe having a suitable shock absorbing function. One example of such an arrangement is disclosed in the specification and drawings of Japanese Patent Application No. 8-18596.
In normal use of the shift lever with the shock absorbing member, as disclosed in Japanese laid-open Patent Publication No. 9-58288, a load (bending stress) is frequently applied to the lever in the bending direction, and it is therefore difficult ensure a sufficiently high durability of the shift lever.
Each of the pipes as disclosed in Japanese laid-open Patent Publication No. 9-58288 and Japanese Patent Application No. 8-18596 is formed of a fiber reinforced plastic material. When, however, the shock absorbing portion expands and ruptures the end portion of the pipe in the direction perpendicular to the axis of the pipe, the maximum breaking load with which the pipe starts breaking or rupturing is undesirably increased if the strength of the pipe end portion is excessively large, thus making it difficult to reduce the deceleration of the passenger to be equal to or lower than the regulation value. It is also important to provide a sufficiently increased average breaking load after the shock absorbing portion starts rupturing in the axial end portion of the pipe, in order to maintain the desired shock absorbing function. Namely, the desired shock absorbing function of the pipe can be accomplished by reducing the maximum breaking load, and increasing the average breaking load, and, in particular, the pipe is required to provide stable breaking characteristics, with significantly reduced variations in the maximum breaking load and the average breaking load.
On the other hand, each of the pipes, as disclosed in Japanese laid-open Patent Publication No. 9-58288 and Japanese Patent Application No. 8-18596, has not been considered well in terms of its material, in order to achieve the above-described shock absorbing function, and it is difficult for the lever mount bracket support structure using the pipe to reduce the maximum breaking load and increase the average breaking load. Furthermore, both the maximum breaking load and average breaking load tend to vary or fluctuate, thus making it impossible to assure stable shock absorbing characteristics.
It is therefore an object of the present invention to provide an energy absorbing member having sufficiently high durability, wherein rupture or breaking takes place with reduced maximum breaking load and increased average breaking load, and wherein variations in both of the loads are sufficiently reduced to ensure stable shock absorbing characteristics.